This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2001-276175, filed Sep. 12, 2001, the entire contents of this application are incorporated herein by reference.
This invention relates to a process for producing microceramic tubes of silicon carbide (SiC) and silicon nitride (SiN) with diameters ranging from several microns to several hundred microns.
Silicon carbide is a material having high heat resistance, high strength and low reactivity and silicon carbide fiber synthesized from silicon-based polymers has already been commercialized. Active research efforts are being made to study SiC composite materials reinforced with SiC fiber.
SiC tubes are currently prepared by one of the following four methods: 1) making hollow fibers by mechanical working; 2) shaping cylinders by CVD (chemical vapor deposition); 3) making use of self-assembly; and 4) spinning hollow fibers from special nozzles.
The fiber diameter that can be realized by the first method which depends on mechanical working is no smaller than several hundred microns and it is difficult to prepare tubes with diameters on the micron order. The second method which depends on CVD involves difficulty in mass production. The third method which depends on self-assembly can only produce tubes with diameters on the nano order. The fourth technique which prepares hollow fibers by spinning is not suitable for melt spinning of organosilicon-based polymers. Thus, no techniques have been established that can produce ceramic tubes with diameters ranging from 10 microns to several hundred microns.
An object, therefore, of the invention is to provide a process by which ceramic tubes with diameters ranging from several microns to several hundred microns can be easily prepared through the steps of applying an ionizing radiation to a silicon-based polymer such that only its surface layer is rendered infusible and then firing the polymer.